Electrode plate of a secondary battery and a secondary battery

ABSTRACT

The present disclosure relates to a secondary battery and an electrode plate. The electrode plate includes a current collector, an active material layer, a conductive structure, and a first protective layer. The current collector includes an insulating layer and a conductive layer disposed on the insulating layer. The conductive layer includes a main body portion and a protrusion portion. A surface of the main body portion facing away from the insulating layer is covered by the active material layer, while a surface of the protrusion portion facing away from the insulating layer is uncovered by the active material layer. The conductive structure is welded to the protrusion portion and thus a welded zone is formed. The first protective layer has elasticity, and is disposed on a side of the protrusion portion facing away from the insulating layer and is located between the welded zone and the active material layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/375,531, filed on Apr. 4, 2019, which claims priority to ChinesePatent Application No. 201821018434.4, filed on Jun. 29, 2018. Thedisclosures of the aforementioned applications are hereby incorporatedby reference in their entireties.

TECHNICAL FIELD

The present disclosure relates to the technical field of battery, and inparticular, relates to a secondary battery and an electrode plate of thesecondary battery.

BACKGROUND

An electrode plate of a secondary battery generally includes a currentcollector and an active material layer coated on a surface of thecurrent collector. In order to improve safety performance of thesecondary battery, an electrode plate 1 can adopt a current collector 11having a multilayer structure. Referring to FIGS. 1 and 2 , the currentcollector 11 includes an insulating layer 111 and conductive layers 112provided on both surfaces of the insulating layer 111, and an activematerial layer 12 is coated on a surface of each conductive layer 112.The conductive layer 112 includes a main body portion 1121 covered bythe active material layer 12 and a protrusion portion 1122 protrudingfrom the active material layer 12. The protrusion portion 1122 togetherwith a part of the insulation layer 111 corresponding to the protrusionportion 1122 constitutes a current guiding portion P. The insulatinglayer 111 insulates the conductive layers 112 disposed on its bothsides, so that current cannot flow between these two conductive layers112. Therefore, the current guiding portion P has a poor current passingperformance In order to improve the current passing performance, aconductive structure 13 is usually welded on the conductive layers 112and thus a welded zone W is formed between the conductive structure 13and the conductive layer 112, so that the current on each conductivelayer 112 converges on the conductive structure 13. Connecting thecurrent guiding portion P and the conductive structure 13 together wouldlead to a large length such that the current guiding portion P and theconductive structure 13 usually have to be bent for saving space. Inaddition, since the welded zone W is unlikely to be bent due to itsgreat rigidity, the bending has to occur at a position lower or higherthan the welded zone W. However, referring to FIG. 1 , when the bendingoccurs at the position lower than the welded zone W, the protrusionportion 1122 can be easily bent to break due to a small thicknessthereof, thereby affecting the current passing performance Referring toFIG. 2 , when the bending occurs at the position higher than the weldedzone W, the welded zone W will still occupy a large space at height,thereby affecting an energy density of the secondary battery.

SUMMARY

In view of the problems in the prior art, the present disclosure aims toprovide a secondary battery and an electrode plate thereof, aiming toenhance the energy density as well as improve safety performance and thecurrent passing performance

According to a first aspect of the present disclosure, an electrodeplate of a secondary battery is provided. The electrode plate includes:a current collector; an active material layer; a conductive structure;and a first protective layer. The current collector includes aninsulating layer and a conductive layer disposed on the insulatinglayer. The conductive layer includes a main body portion and aprotrusion portion connected to the main body portion. A surface of themain body portion facing away from the insulating layer is covered bythe active material layer, and a surface of the protrusion portionfacing away from the insulating layer is uncovered by the activematerial layer. The conductive structure is welded to the protrusionportion and thus a welded zone is formed. The first protective layer haselasticity, and the first protective layer is disposed on a side of theprotrusion portion facing away from the insulating layer and is locatedbetween the welded zone and the active material layer.

In an embodiment, in a thickness direction of the electrode plate, asurface of the first protective layer facing away from the protrusionportion is lower than a surface of the active material layer facing awayfrom the main body portion.

In an embodiment, in a thickness direction of the electrode plate, asurface of the first protective layer facing away from the protrusionportion is closer to the insulating layer than a surface of the activematerial layer facing away from the main body portion.

In an embodiment, the first protective layer is connected to an end ofthe active material layer close to the conductive structure and an endof the conductive structure close to the active material layer.

In an embodiment, the first protective layer is in contact with theprotrusion portion, and the first protective layer has a smaller modulusof elasticity than the protrusion portion.

In an embodiment, the electrode plate further includes a secondprotective layer disposed between the first protective layer and theactive material layer. The second protective layer has a greaterhardness than the conductive layer.

In an embodiment, the second protective layer is connected to the activematerial layer, and the first protective layer is connected to an end ofthe second protective layer away from the active material layer and anend of the conductive structure close to the active material layer.

In an embodiment, the electrode plate further includes a thirdprotective layer covering a surface of the welded zone facing away fromthe protrusion portion. The third protective layer is connect to thefirst protective layer, and is made of a material same as the firstprotective layer.

In an embodiment, the first protective layer extends to edges of bothsides of the protrusion portion in a length direction, and the firstprotective layer has a dimension in a range of 0.1 mm to 4 mm along aheight direction.

According to a second aspect of the present disclosure, a secondarybattery is provided. The secondary battery includes an electrodeassembly. The electrode assembly includes the electrode plate accordingto the first aspect.

In an embodiment, a portion of the insulating layer corresponding to theprotrusion portion and the protrusion portion together form a currentguiding portion. The electrode plate includes a plurality of currentguiding portions and a plurality of conductive structures. The pluralityof current guiding portions is stacked, and every two adjacent currentguiding portions of the plurality of current guiding portions have aconductive structure of the plurality of conductive structurestherebetween. The first protective layer and the protrusion portiondisposed opposite to the first protective layer are both bent withrespect to the main body portion.

The technical solutions according to the present disclosure bringfollowing benefits.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of an electrode plate according to therelated art;

FIG. 2 is another schematic diagram of an electrode plate according tothe related art;

FIG. 3 is a schematic diagram of a secondary battery according to anembodiment of the present disclosure;

FIG. 4 is a schematic diagram of an electrode assembly of a secondarybattery according to an embodiment of the present disclosure;

FIG. 5 is a schematic diagram of an electrode plate according to anembodiment of the present disclosure;

FIG. 6 is another schematic diagram of an electrode plate according toan embodiment of the present disclosure;

FIG. 7 is an enlarged view of the dotted frame shown in FIG. 6 ;

FIG. 8 is a section view along A-A shown in FIG. 7 ;

FIG. 9 is a schematic diagram of the electrode plate shown in FIG. 8 ,where a first protective layer is omitted;

FIG. 10 is a schematic diagram of the electrode plate shown in FIG. 8after the electrode plate is bent;

FIG. 11 is a schematic diagram of an electrode plate according toanother embodiment of the present disclosure; and

FIG. 12 is a schematic diagram of an electrode plate according to yetanother embodiment of the present disclosure.

Reference Signs in Drawings: 1 electrode plate 11 current collector 111insulating layer 112 conductive layer 1121 main body portion 1122protrusion portion 12 active material layer 13 conductive structure 14first protective layer 15 second protective layer 16 third protectivelayer 1B negative electrode plate 2 case 3 top cover 4 electrodeterminal 5 separator 6 connecting piece P current guiding portion Wwelded zone X length direction Y thickness direction Z height direction

DESCRIPTION OF EMBODIMENTS

Referring to FIG. 3 , a secondary battery includes an electrodeassembly, a case 2, a top cover 3, an electrode terminal 4, and aconnecting piece 6.

Referring to FIG. 4 , an electrode assembly includes a positiveelectrode plate 1A, a negative electrode plate 1B and a separator 5. Theseparator is disposed between the positive electrode plate 1A and thenegative electrode plate 1B. The positive electrode plate 1A, theseparator 5 and the negative electrode plate 1B are stacked in sequenceand wound to form a jelly roll-shaped electrode assembly.

The case 2 can have a hexahedral shape or other shape. A cavity isformed inside the case 2 to accommodate the electrode assembly andelectrolyte. The case 2 has an opening at an end through which theelectrode assembly can be placed into the cavity of the case 2. The case2 can be made of a conductive metal material such as aluminum oraluminum alloy, or an insulating material such as plastic.

The top cover 3 is provided on the case 2 and covers the opening of thecase 2 to seal the electrode assembly within the case 2. The electrodeterminal 4 is disposed on the top cover 3. The electrode terminal 4 hasan upper end protruding from an upper side of the top cover 3, and alower end passing through the top cover 3 and extending into the case 2.The connecting piece 6 is disposed in the case 2 and is fixed to theelectrode terminal 4. There are two electrode terminals 4 and twoconnecting piece 6. The positive electrode plate 1A is electricallyconnected to one of the two electrode terminals 4 via one of the twoconnecting pieces 6, and the negative electrode plate 1B is electricallyconnected to the other of the two electrode terminals 4 via the other ofthe two connecting pieces 6.

In the secondary battery according to the present disclosure, at leastone of the positive electrode plate 1A and the negative electrode plate1B is an electrode plate described below.

Referring to FIGS. 5-9 , an electrode plate 1 includes a currentcollector 11, an active material layer 12, a conductive structure 13 anda first protective layer 14. The current collector 11 includes aninsulating layer 111 and a conductive layer 112 disposed on theinsulating layer 111. The conductive layer 112 includes a main bodyportion 1121 and a protrusion portion 1122 connected to the main bodyportion 1121. A surface of the main body portion 1121 facing away fromthe insulating layer 111 is covered by the active material layer 12, anda surface of the protrusion portion 1122 facing away from the insulatinglayer 111 is uncovered by the active material layer 12. The conductivestructure 13 is welded to the protrusion portion 1122 and thus a weldedzone W is formed. The first protective layer 14 has elasticity and isdisposed on a side of the protrusion portion 1122 facing away from theinsulating layer 111 and is located between the welded zone W and theactive material layer 12.

A portion of the insulating layer 111 corresponding to the protrusionportion 1122 together with the protrusion portion 1122 forms a currentguiding portion P. Referring to FIG. 5 , the electrode plate 1 caninclude a plurality of current guiding portions P and a plurality ofconductive structures 13. Once the electrode plate 1 is formed bywinding, the plurality of current guiding portions P of the electrodeplate 1 is stacked, the plurality of conductive structures 13 is opposedto each other, and each two adjacent current guiding portions P have aconductive structure 13 therebetween. Referring to FIG. 3 , theplurality of conductive structures 13 is welded to a connecting piece 6,so that current on the conductive layers 112 on both sides of theinsulating layer 111 converges onto an electrode terminal 4.

Since the current collector 11 of the electrode plate 1 is provided withthe insulating layer 111, the thickness of the conductive layer 112 canbe reduced. When a foreign matter pierces the electrode plate 1, due tothe small thickness of the conductive layer 112, burr produced at aposition of the conductive layer 112 where it is pierced by the foreignmatter is too small to pierce a separator 5, thereby avoiding a shortcircuit and improving the safety performance Referring to FIG. 10 , thecurrent guiding portion P can be bent at the region between the weldedzone W and the active material layer 12, such that the space in heightoccupied by the current guiding portion P and the conductive structure13 can be reduced, thereby enhancing the energy density of the secondarybattery. The first protective layer 14 can protect the protrusionportion 1122 from being broken when being bent, and thus guarantee thecurrent passing performance of the protrusion portion 1122. In themeantime, the first protective layer 14, due to its elasticity, can bebent together with the current guiding portion P, avoiding increasingthe difficulty of bending the current guiding portion P.

After the current guiding portion P is bent, the first protective layer14 and the protrusion portion 1122 disposed opposite to the firstprotective layer 14 are both bent with respect to the main body portion1121. An end of the conductive structure 13 away from the activematerial layer 12 can extend beyond an end of the protrusion portion1122 away from the main body portion 1121, and the exceeding portion canbe bent to reduce the space occupied by the conductive structure 13 in athickness direction Y.

The electrode plate 1 can be formed according to following steps of: 1.applying the active material layer 12 to a surface of the conductivelayer 112 of the current collector 11; 2. rolling the active materiallayer 12 to compact the active material layer 12; 3. performing cuttingto get the protrusion portion 1122 in a desired shape and the portion ofinsulating layer 111 corresponding to the protrusion portion 1122; 4.welding the conductive structure 13 to the protrusion portion 1122 andforming a welded zone W; and 5. applying a paste, such as an insulatingglue, to the region of the protrusion portion 1122 between the weldedzone W and the active material layer 12, thereby forming the firstprotective layer 14 having elasticity after curing of the paste.

The conductive layer 112 fully covers each surface of the insulatinglayer 111. The insulating layer 111 has a thickness of 1 μm to 20 μm.The conductive layer 112 has a thickness of 0.1 μm to 10 μm. Theconductive structure 13 has a thickness of 6 μm to 15 μm. Since theconductive layer 112 is relatively thin, burr formed on the conductivelayer 112 during the cutting process is too small to pierce theseparator 5 having a thickness of dozens of micrometers, therebyavoiding a short circuit and improving safety performance

Referring to FIG. 8 , in the thickness direction Y, a surface of thefirst protective layer 14 facing away from the protrusion portion 1122is lower than a surface of the active material layer 12 facing away fromthe main body portion 1121, i.e., the surface of the first protectivelayer 14 facing away from the protrusion portion 1122 is closer to theinsulating layer than the surface of the active material layer 12 facingaway from the main body portion 1121, so that the first protective layer14 will not result in an increase in an overall thickness of theelectrode plate 1, guaranteeing a high energy density of the secondarybattery.

The first protective layer 14 can be directly disposed on the surface ofthe protrusion portion 1122 facing away from the insulating layer 111 tobe in direct contact with the protrusion portion 1122. Alternatively,the first protective layer 14 also can be disposed on a surface of acoating, which is provided on the surface of the protrusion portion 1122facing away from the insulating layer 111.

The first protective layer 14 has a smaller modulus of elasticity thanthe protrusion portion 1122. Since the first protective layer 14 islocated outside of the protrusion portion 1122, after the currentguiding portion P is bent, an amount of deformation of the firstprotective layer 14 should be larger than an amount of deformation ofthe protrusion portion 1122. If the first protective layer 14 has agreater modulus of elasticity than the protrusion portion 1122, theamount of deformation of the first protective layer 14 will be smallerthan the amount of deformation of the protrusion portion 1122 when thecurrent guiding portion P is bent, which may lead to a relative slide oreven a detachment between the first protective layer 14 and the currentguiding portion P.

In an embodiment, the first protective layer 14 is respectivelyconnected to an end of the active material layer 12 close to theconductive structure 13 and an end of the conductive structure 13 closeto the active material layer 12, so that the first protective layer 14can be simultaneously fixed to the active material layer 12, theconductive structure 13 and the protrusion portion 1122. In this way, abonding force of the first protective layer 14 on the electrode plate 1can be increased, thereby preventing the first protective layer 14 frompeeling off together with the protrusion portion 1122.

In another embodiment, referring to FIG. 11 , the electrode plate 1further includes a second protective layer 15 disposed between the firstprotective layer 14 and the active material layer 12, and the secondprotective layer 15 has a greater hardness than the conductive layer112.

After the active material layer 12 is applied to the conductive layer112, the electrode plate 1 should be rolled to make the active materiallayer 12 thinner, so as to increase the energy density. However, duringthe rolling process, the roller will exert force directly on the activematerial layer 12, but not on the protrusion portion 1122 since theprotrusion portion 1122 of the conductive layer 113 is uncoated with theactive material layer 12. Since the insulating layer 111has a smallermodulus of elasticity than the conductive layer 112, an amount ofdeformation of the insulating layer 111is larger than an amount ofdeformation of the conductive layer 112 under the force of the roller,which can lead to a bulge at the interface between the main body portion1121 and the protrusion portion 1122. A deformation of bugle on theinsulating layer 111 would also result in a bugle of the protrusionportion 1122, so that the protrusion portion 1122 is likely to be bentand crack, thereby degrading the current passing performance of theprotrusion portion 1122. By providing the second protective layer 15,the deformation of the protrusion portion 1122 can be restricted, andthus the protrusion portion 1122 can be prevented from being brokenduring the rolling process and the current passing performance of theelectrode plate 1 can be improved.

The second protective layer 15 has a relative great hardness and thus isunlikely to be bent, so that the current guiding portion P should bebent in the region covered by the first protective layer 14.

The second protective layer 15 is connected to the active material layer12, and the first protective layer 14 is respectively connected to anend of the second protective layer 15 away from the active materiallayer 12 and an end of the conductive structure 13 close to the activematerial layer 12. The first protective layer 14, the second protectivelayer 15 and the conductive structure 13 are connected as a whole, sothat a bonding force of the first protective layer 14 and the secondprotective layer 15 on the electrode plate 1 can be increased, therebypreventing the first protective layer 14 and the second protective layer15 from peeling off together with the protrusion portion 1122. Inaddition, the second protective layer 15 is connected to the activematerial layer 12, so that the second protective layer 15 can cover thejunction between the main body portion 1121 and the protrusion portion1122. In this way, the protrusion portion 1122 can be protected frombeing broken, and the current passing performance of the electrode plate1 can be enhanced.

Referring to FIG. 12 , the electrode plate 1 further includes a thirdprotective layer 16 covering a surface of the welded zone W facing awayfrom the protrusion portion 1122. The rough surface of the welded zone Wfacing away from the protrusion portion 1122 might pierce the separator5, causing a short circuit. The third protective layer 16 can separatethe separator 5 from the surface of the welded zone W, and prevent theseparator 5 from being pierced, thereby improving the safetyperformance.

The third protective layer 16 is connect to the first protective layer14, and is made of a material same as the first protective layer 14.During the forming process of the electrode plate 1, the paste can beapplied to the region of the protrusion portion 1122 located between thewelded zone W and the active material layer 12 as well as to a surfaceof the welded zone W facing away from the protrusion portion 1122, so asto form the first protective layer 14 and the third protective layer 16that are connected with one another after curing of the paste.

Referring to FIG. 7 , the first protective layer 14 extends to edges ofboth sides of the protrusion portion 1122 in a length direction X, so asto maximize a coverage area of the first protective layer 14 and improvethe protection effect of the first protective layer 14. The firstprotective layer 14 has a dimension L1 in a range of 0.1 mm to 4 mmalong a height direction Z.

What is claimed is:
 1. An electrode plate of a secondary battery,comprising: a current collector; an active material layer; a conductivestructure; and a first protective layer, wherein the current collectorcomprises an insulating layer and two conductive layers disposedrespectively on two opposite sides of the insulating layer, a conductivelayer includes a main body portion and a protrusion portion connected tothe main body portion, a surface of the main body portion facing awayfrom the insulating layer is covered by the active material layer, and asurface of the protrusion portion facing away from the insulating layeris uncovered by the active material layer, the conductive structure iswelded to the protrusion portion and thus a welded zone is formed, andthe first protective layer has elasticity, and the first protectivelayer is disposed on a side of the protrusion portion facing away fromthe insulating layer and is located between the welded zone and theactive material layer.
 2. The electrode plate according to claim 1,wherein the first protective layer and the protrusion portion disposedopposite to the first protective layer are both bent with respect to themain body portion.
 3. The electrode plate according to claim 1, whereinin a thickness direction of the electrode plate, a surface of the firstprotective layer facing away from the protrusion portion is closer tothe insulating layer than a surface of the active material layer facingaway from the main body portion.
 4. The electrode plate according toclaim 1, wherein the first protective layer is connected to an end ofthe active material layer close to the conductive structure and an endof the conductive structure close to the active material layer.
 5. Theelectrode plate according to claim 1, wherein the first protective layeris in contact with the protrusion portion, and the first protectivelayer has a smaller modulus of elasticity than the protrusion portion.6. The electrode plate according to claim 1, further comprising a secondprotective layer disposed between the first protective layer and theactive material layer, wherein the second protective layer has a greaterhardness than the conductive layer.
 7. The electrode plate according toclaim 6, wherein the second protective layer is connected to the activematerial layer, and the first protective layer is connected to an end ofthe second protective layer away from the active material layer and anend of the conductive structure close to the active material layer. 8.The electrode plate according to claim 1, further comprising a thirdprotective layer covering a surface of the welded zone facing away fromthe protrusion portion, wherein the third protective layer is connect tothe first protective layer, and is made of a material same as the firstprotective layer.
 9. The electrode plate according to claim 1, whereinthe two conductive layers comprise two protrusion portions, theelectrode plate comprises two first protective layers, each of the twofirst protective layers is disposed on a side of a correspondingprotrusion portion of the two protrusion portions.
 10. A secondarybattery, comprising an electrode assembly, wherein the electrodeassembly comprises an electrode plate, the electrode plate comprising: acurrent collector; an active material layer; a conductive structure; anda first protective layer, wherein the current collector comprises aninsulating layer and two conductive layers disposed respectively on twoopposite sides of the insulating layer, a conductive layer includes amain body portion and a protrusion portion connected to the main bodyportion, a surface of the main body portion facing away from theinsulating layer is covered by the active material layer, and a surfaceof the protrusion portion facing away from the insulating layer isuncovered by the active material layer, the conductive structure iswelded to the protrusion portion and thus a welded zone is formed, andthe first protective layer has elasticity, and the first protectivelayer is disposed on a side of the protrusion portion facing away fromthe insulating layer and is located between the welded zone and theactive material layer.
 11. The secondary battery according to claim 10,wherein the first protective layer and the protrusion portion disposedopposite to the first protective layer are both bent with respect to themain body portion.
 12. The secondary battery according to claim 10,wherein in a thickness direction of the electrode plate, a surface ofthe first protective layer facing away from the protrusion portion iscloser to the insulating layer than a surface of the active materiallayer facing away from the main body portion.
 13. The secondary batteryaccording to claim 10, wherein the first protective layer is connectedto an end of the active material layer close to the conductive structureand an end of the conductive structure close to the active materiallayer.
 14. The secondary battery according to claim 10, wherein thefirst protective layer is in contact with the protrusion portion, andthe first protective layer has a smaller modulus of elasticity than theprotrusion portion.
 15. The secondary battery according to claim 10,further comprising a second protective layer disposed between the firstprotective layer and the active material layer, wherein the secondprotective layer has a greater hardness than the conductive layer. 16.The secondary battery according to claim 15, wherein the secondprotective layer is connected to the active material layer, and thefirst protective layer is connected to an end of the second protectivelayer away from the active material layer and an end of the conductivestructure close to the active material layer.
 17. The secondary batteryaccording to claim 10, further comprising a third protective layercovering a surface of the welded zone facing away from the protrusionportion, wherein the third protective layer is connect to the firstprotective layer, and is made of a material same as the first protectivelayer.
 18. The secondary battery according to claim 10, wherein the twoconductive layers comprise two protrusion portions, the electrode platecomprises two first protective layers, each of the two first protectivelayers is disposed on a side of a corresponding protrusion portion ofthe two protrusion portions.
 19. The secondary battery according toclaim 10, wherein a portion of the insulating layer corresponding to theprotrusion portion and the protrusion portion together form a currentguiding portion, the electrode plate includes a plurality of currentguiding portions and a plurality of conductive structures, the pluralityof current guiding portions is stacked, and every two adjacent currentguiding portions of the plurality of current guiding portions have aconductive structure of the plurality of conductive structurestherebetween, and the first protective layer and the protrusion portiondisposed opposite to the first protective layer are both bent withrespect to the main body portion.
 20. The secondary battery according toclaim 10, wherein the electrode assembly includes a positive electrodeplate, a negative electrode plate and a separator, the separator isdisposed between the positive electrode plate and the negative electrodeplate, and the positive electrode plate, the separator and the negativeelectrode plate are stacked in sequence and wound to form a jellyroll-shaped electrode assembly, at least one of the positive electrodeplate and the negative electrode plate is the electrode plate.